Summary of Work: We are conducting a study to estimate prevalence and risk factors for uterine fibroids (as detected by a standard transabdominal and transvaginal ultrasound examination) in black women compared to nonblacks aged 35-49. Uterine tissue from women having fibroids removed will be studied to identify hormonal charaacteristics, growth factors and genetic changes in the tissue that are associated with fibroid development. Data will be collected from over 800 cases (both ultrasound identified and surgically idenitified cases of leiomyomas) and 200 controls (women found to have no evidence of leiomyomas at ultrasound) from the membership of a health care plan that serves approximately equal numbers of blacks and whites. A telephone interview is used to collect information on demographic factors, medical history, dietary intake, reproductive history, life style factors, and occupational/environmental exposures. Blood is being collected (after fasting) in order to measure lipids, insulin, and potential susceptibility genes. Urine is being collected to measure endogenous gonadotropins. Blood pressure, heart rate, weight, height, and waist-to-hip ratio will be measured. Medical record data will provide descriptive information on nonresponders. Tissue from surgical specimens will be analyzed for growth factors, hormonal conditions, and genetic characteristics of the fibroid.